The present invention relates to synthetic hair used for hair goods such as wigs, hairpieces and weavings and doll hair and a process for preparing the same. More specifically, the present invention relates to synthetic hair which is made of fiber prepared using an acrylic polymer comprising acrylonitrile, vinylidene chloride and a vinyl monomer containing a sulfonic acid group copolymerizable therewith and has favorable surface gloss, curl setting property and hairstylability (property of creating various hairstyles when made into a wig), excellent knot strength and is suitable for preparation of wigs and toupees, and a process for preparing the synthetic hair.
Qualities conventionally demanded in material for synthetic hair are curl shape, appearance such as gloss and coloring, hair care properties such as combing properties and stylability, dye-affinity, hackling properties, curl setting properties, processability for machine sewing and hair implant to skin, volume, texture and flame retardant property.
Of the material for synthetic hair which is currently available, in the case of material for synthetic hair (fiber) of polypropylene or polyester, flame retardant property is poor and in the case of material for synthetic hair using vinyl chloride or vinylidene chloride, dye-affinity and volume per weight unit are poor.
As a typical material with the demanded properties, human hair and synthetic hair comprising acrylic fiber obtained by copolymerizing acrylonitrile and vinyl chloride is known. However, when human hair is used as a material, procuring the material and hair length are problems. Vinyl chloride which is a high pressure gas is industrially difficult to handle and widespread use of the acrylic polymer has been inhibited as preparing the acrylic copolymer is restricted in many ways in terms of equipment. Also, depending on the product, the acrylic fiber obtained by copolymerizing acrylonitrile and vinyl chloride is balanced in gloss, coloring and texture and is flame resistant. However, curl setting properties are faulty as the set curl shape changes over time and improvement in stylability is desired as hairstyles which the stylability of current acrylic fiber cannot achieve are in demand.
On the other hand, using vinylidene chloride instead of vinyl chloride has the advantages of few restrictions in manufacturing equipment, favorable polymerization properties and superior flame retardant property compared to vinyl chloride. When preparing by wet spinning fiber made of an acrylic copolymer obtained by copolymerizing at least 25% by weight of vinylidene chloride, organic solvent is often used as the solvent. However, when a good solvent is used, the spinning solution discharged through the spinneret coagulates by counter diffusion with the coagulation solution causing unevenness in the inner structure of the fiber as the fineness of the fiber increases and as a result, void tends to remain inside the fiber. Consequently, favorable gloss can only be obtained in the case of a fineness of less than 30 decitex.
For example, fiber made of an acrylic copolymer obtained by copolymerizing vinylidene chloride is disclosed in JP-A-48-77122, which suggests a process for preparing fiber in which densifying the fiber structure and improving gloss is attempted by adding water to the spinning solution. However, as the copolymer contains at least 80% by weight of acrylonitrile, flame retardant property is inferior.
Also, JP-A-51-4324 discloses a process for preparing an acrylic fiber which comprises copolymerizing 0.1 to 10% by weight of a monomer in which a sulfonic acid group is introduced into an amide compound containing a vinyl group such as acrylic amide or methacrylic amide. This process attempts to improve gloss in fiber of a thin fineness. However, favorable gloss is not obtained in fiber with a thick fineness which is suitable for hair material. Furthermore, fiber obtained by wet spinning an acrylic copolymer obtained by copolymerizing at least 25% by weight of vinylidene chloride has the disadvantage that processing tends to be difficult as knot strength is weak and breaking of the hair is frequent when implanting hair to prepare a wig or toupee, due to the fiber properties. This tendency is particularly noticeable in thick fineness.
An example of a method for improving knot strength is disclosed in JP-48-61727. This method comprises the following steps. A tow obtained by conventional wet spinning is stretched in a hot water environment, passed through a heating roller and further stretched in a vapor zone filled with saturated vapor. Then, in the vapor zone filled with saturated vapor, using a heating roller having a winding speed slower than that of the previous zone, the tow is wound and passed through a cooling roll. However, by this method, fiber of a thick fineness with favorable gloss could not be obtained under the conditions in which knot strength was satisfactory.
The present inventors believe the reason for this are as described below. That is, usually in wet spinning of fiber in which a good solvent is used, the fiber stretched in a hot water bath is devitrified by the void inside the fiber and so gloss is exhibited in the following step of the heating roller. However, later when the tow is relaxed in a dampened state under a saturated vapor environment, the void which has vanished reappear and consequently a decrease in gloss occurs. More specifically, as described above, the void within the fiber tends to remain as the fineness becomes thicker as unevenness in coagulation becomes noticeable and the number and size of the void tends to increase. The developed voids are mainly stretched out by stretching in a hot water bath and the diameter of the void area present perpendicular to the fiber axis become small. Furthermore, due to the shrinking force and collapsing effect by heating which occur from heating to dry, the number and size of the void seems to have decreased. However, in this method, because the tow is in a wet state when relaxing, the tow is plasticized by the influence of excess hot water on the fiber surface and activity of the polymer molecules are advanced, revealing again the voids within the fiber which were collapsed by heating. A decrease in gloss is thought to occur because diffused reflection due to these voids occurs inside the fiber.
The synthetic fiber having as the main component acrylonitrile and vinylidene chloride, which is superior in flame retardant property and has few restrictions for preparing the copolymer, has the above technical problems. Therefore, in reality, quality in thick fiber of more than 30 decitex could not be fulfilled. As a result, development of toupees and wigs, in which thick fiber is used, favorable gloss is demanded and at least a certain knot strength is required, was thought to be limited.
That is, the object of the present invention is to provide synthetic hair made of fiber comprising an acrylic copolymer obtained by copolymerizing acrylonitrile and vinylidene chloride as the main components, which has favorable gloss, which is a property desired in material for synthetic hair, knot strength improved to at least a certain strength and good processability for wigs and toupees.
Furthermore, the present invention aims to provide synthetic hair which has good curl setting properties and high hairstylability as synthetic hair used in hair goods and enables planning of a wide variety of projects by using as material for synthetic hair in hair goods.
In order to obtain the above synthetic hair, a polymer solution comprising a polymer obtained with acrylonitrile and vinylidene chloride as the main components and a good solvent is spun. Wet spinning, in which the amount of solvent remnant in the fiber is less than in dry spinning, may be employed. At this time, in order to make the structure of coagulated fiber during wet spinning even compared to fiber of a thin fineness, two methods of (1) improvement in the coagulation properties of the polymer and (2) adjusting the spinning solution can be combined. As a result, the balance between the solvent diffusion from the spinning solution to the coagulant bath and the coagulant, that is water, diffusion from the coagulant bath to the spinning solution is suitably adjusted, to improve gloss in fiber of thick fineness.
Also, the desired synthetic hair was found by attempting to improve knot strength by imparting a specific relaxation ratio after drying in order to improve processability for wigs and toupees and the present invention was reached.
That is, the present invention relates to synthetic hair comprising fiber obtained from an acrylic polymer comprising 40 to 74% by weight of acrylonitrile, 25 to 59% by weight of vinylidene chloride and 1 to 5% by weight of a vinyl monomer containing a sulfonic acid group copolymerizable therewith, wherein the fiber has a gloss contrast of at least 0.88 and an average filament fineness of 30 to 100 decitex.
In the synthetic hair, the fiber preferably has a knot strength of at least 0.5 cN/decitex.
In the synthetic hair, the fiber is preferably obtained by wet spinning using a good solvent.
The good solvent is preferably at least one member selected from the group consisting of dimethylformamide (hereinafter DMF), dimethylacetamide (hereinafter DMAc) and dimethyl sulfoxide (hereinafter DMSO).
The present invention also relates to a process for preparing the synthetic hair which comprises the steps of preparing a spinning solution containing, in a polymer solution of an acrylic polymer comprising 40 to 74% by weight of acrylonitrile, 25 to 59% by weight of vinylidene chloride and 1 to 5% by weight of a vinyl monomer containing a sulfonic acid group copolymerizable therewith and a good solvent, 3 to 25 parts by weight of water based on 100 parts by weight of the polymer, forming fiber by wet spinning the spinning solution, conducting drawing treatment so that the total drawing ratio of the fiber becomes 2.5 to 12 times and conducting relaxing treatment so that the total relaxation ratio of the fiber becomes at least 15%.
In the process, the relaxing treatment is preferably divided into two or more times.
In the process, the relaxing treatment is preferably conducted in a vapor atmosphere of a pressurized and/or overheated state after drying the fiber.
In the process, the vapor atmosphere preferably has a temperature of 120xc2x0 to 200xc2x0 C.